Process of manufacturing a magnetic read head

ABSTRACT

A magnetic read head with reduced side reading characteristics is described. This design combines use of a current channeling layer (CCL) with stabilizing longitudinal bias layers whose magnetization direction is canted relative to that of the free layer easy axis and that of the pinned layer (of the GMR). This provides several advantages: First, the canting of the free layer at the side region results in a reduction of side reading by reducing magnetic sensitivity in that region. Second, the CCL leads to a narrow current flow profile at the side region, therefore producing a narrow track width definition. A process for making this device is described. Said process allows some of the requirements for interface cleaning associated with prior art processes to be relaxed.

FIELD OF THE INVENTION

The invention relates to the general field of read heads for magneticdisks with particular reference to enhancing narrow track widthdefinition.

BACKGROUND OF THE INVENTION

The read element in a magnetic disk system is a thin slice of material,located between two magnetic shields, whose electrical resistivitychanges on exposure to a magnetic field. Magneto-resistance can besignificantly increased by means of a structure known as a spin valve(SV). The resulting increase (known as Giant magneto-resistance or GMR)derives from the fact that electrons in a magnetized solid are subjectto significantly less scattering by the lattice when their ownmagnetization vectors (due to spin) are parallel (as opposed toanti-parallel) to the direction of magnetization of the solid as awhole.

The key elements of a spin valve structure are two magnetic layersseparated by a non-magnetic layer. The thickness of the non-magneticlayer is chosen so that the magnetic layers are sufficiently far apartfor exchange effects to be negligible but are close enough to be withinthe mean free path of conduction electrons in the material. If the twomagnetic layers are magnetized in opposite directions and a current ispassed through them along the direction of magnetization, half theelectrons in each layer will be subject to increased scattering whilehalf will be unaffected (to a first approximation). Furthermore, onlythe unaffected electrons will have mean free paths long enough for themto have a high probability of crossing the non magnetic layer. Oncethese electrons have crossed the non-magnetic layer, they areimmediately subject to increased scattering, thereby becoming unlikelyto return to their original side, the overall result being a significantincrease in the resistance of the entire structure.

In order to make use of the GMR effect, the direction of magnetizationof one the layers must be permanently fixed, or pinned. The other layer,by contrast, is a “free layer” whose direction of magnetization can bereadily changed by an external field (such as that associated with a bitat the surface of a magnetic disk). Structures in which the pinned layeris at the top are referred to as top spin valves. Similarly, in a bottomspin valve structure the pinned layer is at the bottom.

Shown in FIG. 1, is a schematic cross-section of a lead overlaid spinvalve head. Seen there is GMR stack 11 that rests on insulatingsubstrate 10 and is protected by capping layer 12. Although not directlyconnected to the GMR effect, an important feature of any spin valvestructure is a pair of longitudinal bias stripes 13 that are permanentlymagnetized in a direction parallel to the long dimension of the device.Also seen in FIG. 1 are conductive leads 15 with tantalum underlayer 14.This design is considered to be one of the best candidates for narrowtrack width reading because of its high signal output and goodstability. However, one big drawback is its track width broadening. Thispoor track width definition is due to the wide spreading current profilefrom lead to GMR stack, partly due to the high resistivity Ta underlayer14 in the lead and partly due to the oxidation of Ta in the overlaidregion during etching and annealing processes.

In a previously filed application, (Ser. No. 09/993,402 Nov. 6, 2001),it was described how a current channeling layer(CCL) 25 may be insertedbetween the lead underlay 14 and the GMR stack to minimize currentspreading (see FIG. 2). The use of a CCL can effectively reduce thecurrent spread caused by the Ta underlayer, but interface oxidationstill remains a problem.

Another previously filed application (Ser. No. 09/931,155 Aug. 17, 2001)disclosed an approach wherein a canted soft adjacent ferromagnetic layer33 (pinned by an antiferromagnetic layer 34) was used to stabilize thestructure, as shown in FIG. 3. In this scheme, the magnetostatic fieldfrom soft adjacent ferromagnetic layer (SAL) 33, which is exchangecoupled to antiferromagnetic film 34, is used to provide horizontalstabilization to the layer. The magnetization in the SAL is cantedtoward the transverse direction. The magnetostatic field generated bysuch a canted SAL layer biases the free layer magnetization in thecenter region along the horizontal direction while biasing themagnetization in the side region along the transverse direction. This isschematically illustrated in FIG. 6 where free layer 116, pinned layer117, and seed layer 118 are seen.

The net effect of using a canted SAL is that the side region of the freelayer has less flux sensitivity because of its transverse orientation.The requirement of interface cleaning is therefore significantly relaxedcompared to the structure shown in FIG. 1. However, due to the highresistivity of AFM layer 13 and Ta underlayer 14, the current spreadingis significant. During the actual manufacture of heads, the thicknessand canting angle of the SALs may vary, due to processing variations,causing the bias field from the SALs to vary as well. In particular, ifthe bias field from the SAL is not large enough to pin the magnetizationin the wing region, side reading will still occur.

A routine search of the prior art was performed with the followingreferences of interest being found:

In U.S. Pat. No. 5,493,467, Cain et al. show a process for an MR with acanted pinning layer as do U.S. Pat. No. 4,967,298 (Mowry) and U.S. Pat.No. 6,188,495 (Wiitala). U.S. Pat. No. 5,637,235 (Kim et al.) and U.S.Pat. No. 6,292,335 B1 (Gill) are related patents.

SUMMARY OF THE INVENTION

It has been an object of at least one embodiment of the presentinvention to provide a read head for a magnetic disk system.

Another object of at least one embodiment of the present invention hasbeen that said read head display minimum track width broadening.

Still another object of at least one embodiment of the present inventionhas been that the free layer portion of the GMR immediately outside theread gap have less flux sensitivity relative to designs of the priorart.

Yet another object of at least one embodiment of the present inventionhas been to provide a process for manufacturing said read head.

A further object of at least one embodiment of the present invention hasbeen that said process allow some of the requirements for interfacecleaning associated with prior art processes, to be relaxed.

These objects have been achieved by combining use of a currentchanneling layer (CCL) with stabilizing longitudinal bias layers whosemagnetization direction is canted relative to that of the free layereasy axis and that of the pinned layer (of the GMR). This design offersseveral advantages: First, the canting of the free layer at the sideregion results in the reduction of side reading by reducing magneticsensitivity in that region. Second, the CCL leads to a narrow currentflow profile at the side region, therefore producing a narrow trackwidth definition. A process for making this device is described. Saidprocess allows some of the requirements for interface cleaningassociated with prior art processes to be relaxed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a lead overlay read head of the prior art.

FIG. 2 shows the structure of FIG. 1 with an added current channelinglayer.

FIG. 3 is FIG. 1 with an added soft adjacent layer and no longitudinalbias stripe.

FIG. 4 shows the starting structure for the process of the presentinvention.

FIG. 5 shows how liftoff is used to form the soft adjacent layers.

FIG. 6 is a plan view illustrating how the direction of magnetization inthe soft adjacent layers is canted relative to the pinned and freelayers of the GMR.

FIG. 7 illustrates the final structure of the process of the presentinvention.

FIG. 8 is a plot of percent current in the GMR as a function of distancefrom its edge, showing that very little GMR current originates outsidethe read gap.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

We now describe a process for manufacturing the structure of the presentinvention. Referring to FIG. 4, the process begins with the provision ofa magnetic shield layer (not shown) on which is dielectric layer 10. GMRstack 11 is then formed on layer 10 followed by the deposition ofcapping layer 42. This capping layer was Ta, or FeTa and it wasdeposited to a thickness between about 10 and 50 Angstroms. Then, as afirst key feature of the invention, current channeling layer 45 isdeposited onto capping layer 42. For this current channeling layer weused gold, copper or nickel and it was given a thickness between about20 and 100 Angstroms. It is important to note here that if inclusion oflayer 45 was the only novel feature of the present invention, great carewould need to be exercised to ensure that no oxidation of layer 42occurred prior to the deposition of 45. However, additional features ofthe invention, that will be described below, allow the conditions ofinterface cleaning to be considerably more relaxed.

Referring now to FIG. 5, pedestal 56 of a light sensitive material isformed on current channeling layer 45 using conventionalphotolithographic methods. The width of pedestal 56 will determine thewidth of the read track (between about 0.1 and 0.5 microns) while itsheight must exceed the total thickness of all layers deposited on itprior to its removal later on.

Next, after using IBE (ion beam etching) to remove surface contaminantsfrom layer 45, soft magnetic layer 53 is deposited to a thicknessbetween about 50 and 100 Angstroms, followed by deposition ofantiferromagnetic layer 54. For the soft magnetic layer we used NiFe orCoFe while for the antiferromagnetic layer we used any of PtMn, NiMn,IrMn, or PtPdMn. The structure is then annealed in a magnetic field soas to give soft magnetic layer 53 a magnetization direction that isbetween that of the GMR's pinned layer that of the easy axis of the freelayer (of the GMR), subtending an angle of between about 30 and 70degrees relative to said easy axis direction. Annealing was performed ata temperature between about 150 and 250° C. for about 10 hours in amagnetic field of between about 100 and 200 oersted. By thus canting thedirection of the bias stabilization we also relax the requirements forinterface cleaning prior to depositing current channeling layer 45. Thisis because of the reduction in side reading at the free layer wingregion.

The process continues with the deposition, in succession, onantiferromagnetic layer 54, tantalum layer 14, conductive lead layer 15(typically gold to a thickness between about 150 and 400 Angstroms), andsecond tantalum layer 55. A second dielectric layer is then deposited toa thickness between about 150 and 500 Angstroms onto upper tantalumlayer 55 and pedestal 56 is then selectively removed. This causes allmaterials that had been deposited onto the pedestal to be lifted off sothat soft magnetic layer 53 (and all layers above it) are separated intotwo opposing halves separated by the designated track width.

Finally, as seen in FIG. 7, using dielectric layer 57 as a hard mask,all exposed portions of current channeling layer 45 are removed while atthe same time oxidizing any exposed portions of the capping layer. Thus,in FIG. 7, portion 42 a remains metallic while portion 42 b is convertedto its oxide. RIE (reactive ion etching) was used for removing layer 45and oxidizing part of layer 42.

FIG. 8 illustrates the effectiveness of layer 45 by plotting thepercentage of current passing through the GMR stack as a function ofdistance from the overlap region. Curve 81 is for a structure without acurrent channeling layer while curve 82 is with one. As can be seen, forthe prior art structure (curve 81) the current is already at about 50%of its value in the GMR at a distance of about 0.12 microns from theedge whereas for curve 82 this level is not reached until about 0.05microns from the GMR edge.

What is claimed is:
 1. A process for manufacturing a magnetic read headhaving a track width, comprising: providing a magnetic shield layer anddepositing thereon a first dielectric layer; on said first dielectriclayer, depositing a GMR stack that includes a pinned layer that has beenmagnetized in a first direction and a free layer that has an easy axisin a second direction; on said GMR stack, depositing a capping layer; onsaid capping layer depositing a current channeling layer underconditions of relaxed interface cleaning; on said current channelinglayer, depositing and then patterning a layer of photosensitive materialto form a pedestal whose width defines said track width; on saidpedestal and said current channeling layer, depositing a soft magneticlayer; on said soft magnetic layer, depositing an antiferromagneticlayer and then annealing in a magnetic field whereby said soft magneticlayer has a magnetic moment that is about 2-4 times that of said freelayer and is magnetized in a third direction that is between said firstand second directions, thereby relaxing requirements for interfacecleaning; on said antiferromagnetic layer, depositing, in succession, afirst layer of tantalum, a conductive lead layer, and a second layer oftantalum; on said second layer of tantalum, depositing a seconddielectric layer; then selectively removing said pedestal therebylifting off all material deposited on said pedestal and forming twoopposing soft adjacent layers; and using said second dielectric layer asa hard mask, removing all exposed portions of said current channelinglayer and oxidizing any exposed portions of said capping layer.
 2. Theprocess described in claim 1 wherein the step of depositing a GMR stackfurther comprises: depositing a seed layer; on said seed layer,depositing a pinning layer; on said pinning layer, depositing saidpinned layer; on said pinned layer depositing a non-magnetic spacerlayer; and on said spacer layer, depositing said free layer.
 3. Theprocess described in claim 1 wherein said third direction subtends anangle of between about 30 and 70 degrees relative to said seconddirection.
 4. The process described in claim 1 wherein the step ofannealing said stripes in a magnetic field further comprises heating ata temperature between about 150 and 250° C. for about 10 hours in amagnetic field of between about 100 and 200 oersted.
 5. The processdescribed in claim 1 wherein said soft magnetic layer is selected fromthe group consisting of NiFe and CoFe.
 6. The process described in claim1 wherein said soft magnetic layer is deposited to a thickness betweenabout 40 and 100 Angstroms.
 7. The process described in claim 1 whereinsaid antiferromagnetic layer is selected from the group consisting ofPtMn, NiMn, IrMn, and PtPdMn.
 8. The process described in claim 1wherein said capping layer is selected from the group consisting of Taand FeTa.
 9. The process described in claim 1 wherein said capping layeris deposited to a thickness between about 10 and 50 Angstroms.
 10. Theprocess described in claim 1 wherein said current channeling layer isselected from the group consisting of gold, copper, and nickel.
 11. Theprocess described in claim 1 wherein said current channeling layer isdeposited to a thickness between about 20 and 100 Angstroms.
 12. Theprocess described in claim 1 wherein said conductive lead layer is gold.13. The process described in claim 1 wherein said conductive lead layeris deposited to a thickness between about 150 and 400 Angstroms.
 14. Theprocess described in claim 1 wherein said read head track width isbetween about 0.05 and 0.5 microns.
 15. The process described in claim 1wherein said second dielectric layer is alumina.
 16. The processdescribed in claim 1 wherein said second dielectric layer is depositedto a thickness between about 150 and 500 Angstroms.
 17. The processdescribed in claim 1 wherein the step of removing all portions of saidcurrent channeling layer further comprises removing said currentchanneling layer through reactive ion etching followed by oxidizing saidcapping layer.